A. when supply voltage fluctuates
B. when load varies
C. when power factor is unity
D. motor is under loaded
A. the supply voltage and the back e.m.f.
B. magnetising current and back e.m.f.
C. the rotating stator flux and rotor poles
D. none of the above
A. of reducing number of slip rings on the rotor
B. armature is associated with large power as compared to the field circuits
C. of difficulty of providing high voltage insulation on rotor
D. all of the above reasons
A. pony motor
B. D.C. compound motor
C. providing damper winding
D. any of the above
A. the increased load has to take more current
B. the rotor by shifting its phase backward causes motor to take more current
C. the back e.m.f. decreases causing an increase in motor current
D. the rotor strengthens the rotating field casuing more motor current
A. stator supply is relieved of responsibility of producing magnetic field
B. mechanical load on the motor can be adjusted
C. synchronous motor runs at synchronous speed
D. synchronous motor has large air gap
A. leading
B. lagging
C. unity
D. zero